In triggering a strike on an airfield in war-ravaged Syria early Friday, U.S. President Donald Trump significantly reversed many of his previous publicly stated positions on U.S. intervention in Syria. Trump campaigned on an isolationist platform, and in years past, spoke directly against getting involved in the Syrian conflict.

But his policy shifted in the wake of a deadly chemical weapons attack on Tuesday, in the opposition-held northern Syrian town of Khan Sheikhoun killed dozens of people, including at least 11 children.

Here鈥檚 a look at Trump鈥檚 latest policy on U.S. military intervention in Syria鈥檚 six-year civil war, and how it has shifted over the years:

Just last week, U.S. Secretary of State Rex Tillerson publicly stated that Syrian President Bashar Assad鈥檚 political future would be 鈥渄ecided by the Syrian people,鈥� indicating an arm鈥檚-length approach to the Syrian crisis by the U.S.

Then on Thursday, Tillerson told reporters that there is 鈥渘o doubt鈥� that Assad was 鈥渞esponsible鈥� for the chemical attack, and spoke about what role the U.S. is prepared to take in removing him from power.

鈥淭he process by which Assad would leave is something that I think requires an international community effort,鈥� Assad said, adding the first step would be to defeat ISIS within Syria before working with international partners 鈥渢hrough a political process that would lead to Assad leaving.鈥�

Trump appears to have reached a turning point this week, when he saw the images of victims from the Khan Sheikhoun attack.

Just days after members of Trump鈥檚 administration signalled that Assad鈥檚 removal from office was not a priority, the president said Wednesday at the White House that the attack 鈥渉ad a big impact鈥� on him.

鈥淢y attitude towards Syria and Assad has changed very much,鈥� he said.

Speaking about the U.S. airstrike and chemical attack on Thursday night, Trump appeared emotional, telling reporters: 鈥淓ven beautiful babies were cruelly murdered in this very barbaric attack.

鈥淣o child of God should ever suffer such horror.鈥�

Long before Trump was a political player, he criticized then-U.S. President Barack Obama for considering U.S. action in Syria.

In tweets dating back to 2013, Trump suggested that 鈥渧ery bad things will happen鈥� if Obama authorized U.S. military action in Syria:

Congressional approval

In ordering the missile strike Thursday, Trump did not seek the congressional approval he insisted then-president Barack Obama should secure before triggering similar action in 2013. Proceeding without that approval, Trump said at the time, would be a 鈥渂ig mistake.鈥�

鈥榊ou just act鈥�

Not all of Trump鈥檚 messages have been inconsistent. The action taken by the commander-in-chief in Syria on Friday is in keeping with at least one major element of pronouncements on military strategy, says Dakota Wood, a senior defence researcher at U.S. conservative think-tank, the Heritage Foundation.

鈥淒uring the campaign season, then-nominee Trump was saying, 鈥榊ou don鈥檛 telegraph or tell people what you鈥檙e going to do, you just act,鈥欌�� Wood told 麻豆影视 Channel on Friday.

鈥淎nd so here within 48 hours or so of this chemical attack, the president directed his staff to come up with a plan and they executed that plan in the dead of night.鈥�

Wood said that the 鈥渞eality鈥� a world leader faces when they are elected to office is 鈥渇ar different鈥� than the view from the campaign trail.

鈥淭his happens for every president that comes into office. What they want to have happen, what the current situation is domestically or in foreign policy, is far different than the reality they face when they get into the office.鈥�

鈥淲orld War 3鈥�

And so it may have seemed bizarre to some when it might have appeared as though Trump was following the advice of Hillary Clinton, the election rival he repeatedly said, on the campaign trail, would throw 鈥渢he Middle East into turmoil鈥� with her foreign policies.

鈥淲e鈥檙e spending $6 trillion dollars on wars in the Middle East, while our own country falls into total disrepair,鈥� Trump said in a statement on his . 鈥淣ow Hillary wants to start a shooting war in Syria, in conflict with a nuclear-armed Russia, which could lead to World War 3.鈥�

Just hours before the U.S. airstrike on the airbase in Syria Thursday, Clinton spoke at the 鈥淲omen in the World鈥� summit in New York, calling on the U.S. to 鈥渢ake out鈥� Assad鈥檚 airfields and 鈥減revent him from being able to use them to bomb innocent people and drop sarin gas on them.鈥�